Homework Help: Expected Value Probability

1. Feb 15, 2012

lina29

1. The problem statement, all variables and given/known data

A computer code consists of two blocks written independently by two programmers. Each block contains no errors with probability 0.6, one error with probability 0.3, and two errors with probability 0.1.
a. What is the probability that there are more errors in the first block than in the second block?
b. What is the probability that two blocks have an equal number of errors?
c. Compute the expected number of errors in the 1st block.
d. Let Z be the total number of errors in the code. Use your answer in (c) to find E(Z).

2. Relevant equations
For A-.27
B- .46
C- .5

All of which were correct

3. The attempt at a solution
I just don't understand what part d is asking am I supposed to compute the expected number of errors in the 2nd block (.5) and then add it with the first block getting .10

or is there another approach?

2. Feb 15, 2012

Dick

Well, .5+.5 isn't equal to 0.10.

3. Feb 15, 2012

lina29

sorry I knew that :) I meant 1. would that be correct?

4. Feb 15, 2012

Dick

I think so. Expected total number of errors is the sum of the expected number of errors in the two blocks.